CHICAGO — The Mets are a good baseball team. Not great. Good. They should be good enough to give their fans reason to follow them in September.

Not good enough, though, to toss away an outstanding performance from their ace. Not good enough, it’s looking, to thrive amidst a slew of injuries.

Not good enough, surely, to fall victim to the conventional yet twisted thinking that plagues too many managers when they get into the late innings of a road game.

In dropping their third straight game to the Cubs Wednesday night, 2-1 at a freezing Wrigley Field, the Mets (20-14) saw their National League East lead over the Nationals (19-16) dwindle to a game and a half. It shouldn’t be too much longer now before the Nationals, 9-6 victors over the Diamondbacks in Arizona, kick the Mets out of the division penthouse.

“We’re just not giving any of our guys any room to wiggle,” Terry Collins said in a quiet visitors clubhouse. The manager himself, too, has little room for error, thanks to the Mets’ dormant offense, and his strategy backfired when the Cubs walked off with the win — thanks to a bases-loaded walk issued by Jeurys Familia to Chris Coghlan — in the bottom of the ninth.

The Mets couldn’t capitalize on a brilliant performance by Matt Harvey, who pitched seven shutout innings while allowing just three hits, walking two (one intentionally) and tying his season high with nine strikeouts. Harvey hurt his own cause by failing to lay down a bunt with Dilson Herrera on first base and one out in the seventh, popping the ball up and permitting Cubs first baseman Anthony Rizzo to let it drop and execute an easy, inning-ending double play. The more experienced batsmen on Harvey’s side didn’t fare much better against Cubs starter Jason Hammel, breaking a scoreless tie with one and only one run in the top of the sixth. The Mets have now scored three runs or less in 13 of their last 18 games, during which they are 7-11.

Matt Harvey bunts into a double play in the seventh inning of the Mets’ 2-1 loss to the Cubs Wednesday night.AP

No quarrel here with Collins for lifting Harvey after seven innings and 100 pitches. The team must utilize caution in managing the big right-hander as he returns from Tommy John surgery. Instead, it was the deployment of Familia, the successful first-year closer, which raised eyebrows.

Harvey’s status as the game’s winning pitcher ended just three batters into his absence, as Mets setup man Carlos Torres took the mound for the eighth inning and gave up a one-out single to Addison Russell, threw a wild pitch that moved Russell to second and served up the tying single to Dexter Fowler, who ran himself into an out between first and second in an effort to ensure Russell would score from second.

To start the ninth, Collins went back to Torres, who continued to struggle by serving up singles to Rizzo and Starlin Castro, the latter advancing pinch-runner Matt Szczur to third, before intentionally walking Miguel Montero.

And with the game all but over — bases loaded, no outs — this is when Collins called upon Familia.

“It’s a tough situation,” Familia said. “You just want to go in there and keep the ball down. I’m looking for a ground ball, a double play.” He struck out Jorge Soler before walking Coghlan on five pitches.

“I was going to bring him on in the eighth inning,” Collins said of Familia. “If we got Fowler out, I was going to bring him in for a four-out save. But when they tied the game, then you’ve got to get a ground ball [in the ninth]. … He’s the best ground-ball guy I’ve got.”

When I asked Collins whether he considered inserting Familia to start the ninth inning — after all, Torres hardly dominated the eighth — the manager said, “No, no. I did not, because No. 1, … we certainly were trying to hope he would pitch one inning instead of another inning. You’re asking for a two-inning save, and that’s something we haven’t done.”

It’s good that Collins is thinking about preserving Familia, whose 18 games tie him with a handful of other pitchers for third most in the major leagues this year. So how about throwing Familia for just the ninth inning to preserve the tie and rolling the dice on someone else to either keep the game tied or protect the lead in the 10th?

Because of the dilapidated state of the Mets’ bullpen, such a process might have led to the same result. Nevertheless, wouldn’t it have been better for the Mets to fire their best relief bullet in a more optimal situation than bases loaded and none out?

You could point fingers nearly everywhere in the Mets’ universe. For sure, that 13-3 start is a distant memory, and this group is no longer pointing toward greatness.